[bluecalm]

You will not burn 3000 kcal in 40 minutes of gym effort. Even burning 1000kcal in an hour requires serious fitness and burning 1200 is elite athlete level max effort for a full hour.

Calories burnt by walking, assuming flat surface are decently approximated by (distance_in_km x weight) formula so it is possible to burn a lot in 4-5 hours of walking but quite unlikely to hit 3000 unless you're very fit.

[the_snooze]

Going by my fitness tracker, a 1-hour 900kcal gym session is absolutely intense. On the few times I've hit that mark, I'm laid out on the ground and probably need to take it easy the next day.

More realistically, I hit 600-700kcal per session.

[ndsipa_pomu]

I've burnt over 1000kcal in an hour cycling and I'm over 50 and not super-fit. A few hills can make all the difference as it's difficult to be lazy whilst grinding your way up-hill.

[bluecalm]

1000kcal in an hour is around 277 Watts for an hour. There are very few people who can sustain that without serious dedication and long hours for months/years.

[chneu]

Be aware the caloric estimates on gym equipment are like 20% over estimated.

[pandaman]

1000 kcal per hour is 278w FTP if using common convention of 1 cal = 1 j of work (assuming ~20% COP). A lot of people who are very fit dream of such an FTP.

[ndsipa_pomu]

Well, looking at average ranges, 278w FTP would put me in the top 40% or so, which I would consider is reasonably average. Also, I'm reasonably heavy (around 100kg), so that probably makes it easier to put out some power whilst also meaning that I'm slow up the hills.

https://www.cyclinganalytics.com/blog/2018/06/how-does-your-...

[pandaman]

That's a) self-reported and b) among cyclists who track their power i.e. have power-meter equipped bicycle and a head unit to record stats. Self-reporting inflate the numbers by itself but, since most people don't actually have a power meter or/and don't bike, that group is made from quite fit people by selection.

[spacemadness]

I think they mean all day calorie burn, not active burn.

[bluecalm]

Yeah but then they will not get close to what they can burn with 4 hours of walking by doing a 40 minutes gym session.

[bryanlarsen]

The delta is pretty close. Walking is ~200 calories / hour, but sitting is ~100/hr, so the delta is 100/hr. So 4 hours of walking might be as little as an excess of 400. cf a gym workout of 500/hr is also an excess of 400.

IOW, the total calorie burn in a day that includes 4 hours of walking is likely relatively comparable to the total calorie burn in a day that includes an hour of gym time.

[bluecalm]

Walking 5km/h at 70kg is 350kcal/hour. If you are heavy and unfit then it will maybe be 3km/h at 90kg 270kcal/hour but then someone that unfit is not going to be able to burn 500kcal in an hour in a gym anyway.

>>IOW, the total calorie burn in a day that includes 4 hours of walking is likely relatively comparable to the total calorie burn in a day that includes an hour of gym time.

It's a good point about the delta (the estimations are for a total burnt during activity not extra) but I don't think you can get the numbers close. People greatly overestimate how much you burn during gym session as well unless they are already very fit and move constantly during that session.

[const_cast]

I would think the more fit you are, the less calories you’re going to burn per unit of work. Because your body is more efficient.